Method and apparatus for making antennas with ferrite cores



July 7, 1959 F. E. SINGELMAN 2,893,651

METHOD AND APPARATUS FOR MAKING ANTENNAS WITH FERRITE comes Filed April 27, 1955 FREQUENCY 4 60 worsQmtc j I T mmvron FEED E. SINGELMAN HIS ATTOENEY United States Patent METHOD AND APPARATUS FOR MAKING WITH FERRTIE CORES Fred E. Singelman, Palatine, Ill., assignor to IAdmiral Corporation, Chicago, 111., a corporation of Delaware 'Application April 27, 1955, Serial No. 504,255 13 Claims. (Cl. 242-9) This invention relates to methods and apparatus for manufacturing antennas for radio receivers.

Heretofore it has been proposed to provide antennas for radio receivers wherein a core of ceramic iron, known in the art as Ferrite, has wound thereon a number of turns of wire to provide a predetermined inductance which together with a variable capacity forms a resonant circuit for tuning in signals of predetermined frequencies. Such a device is commonly called an iron core antenna and is used in place of a conventional loop antenna. Such an' antenna has certain advantages over previous antennas in that it takes up less space, has a higher signal to noise ratio and in many instances is less expensive to manufacture as well as to install.

Previously such antennas were constructed with a certain number of turns of wire to provide what was believed to be the proper inductance for the particular circuit in which it was placed. It was found that the inductance varied however and therefore it was customary to remove turns, spread the turns or move some of the turns closer together to decrease or increase the inductance after the antenna was installed in the receiver and to enable the inductance to be properly determined for the frequency spectrum that was being tuned and for eifecting proper tracking of the oscillator and antenna circuit.

By the present invention it is possible to determine the exact amount of wire to be wound in the core with sucha degree of accuracy that the need for separating or adjusting the turns in the final assembly is substantially completely eliminated. This decreases the amount of labor necessary to properly balance the antenna to the particular receiver with a resultant decrease in cost due to labor, and an increase in production.

Briefly, my invention comprises winding the wire on the core wherein the wire on the core provides an inductance which is included in an oscillatory circuit, the frequency of the oscillation being continuously measured until a predetermined frequency is indicated after which the winding operation is stopped, because the inductance is now the proper amount necessary to provide the proper antenna for inclusion in the receiver being manufactured.

The wire is then severed and secured in place to prevent it unwinding fromthe core. Thus the exact inductance is obtained in spite of the fact that variables such as core material, Wire size and spacing may be present. Y

For a further andmore comprehensive understanding of my invention reference will be had to the accompaying drawings which illustrate the description of the invention and wherein:

Fig. 1 is a schematic view of an apparatus by means of which the invention may be carried out;

Fig. 2 is a schematic of the" oscillator'circuit and the accompanying means for indicating the frequencies.

Throughout the drawings like parts have been designated by like reference characters.

j As best illustrated in Fig. 1, the wire, which is insulated and comes to the manufacturer on reels or spools 10 which spool is supported on a shaft 11 and brackets 12 in such a manner that the wire may easily be drawn 0E of the spool.

2,893,651 Patented July 7, '1959 The wire then passes through a friction device 14 which holds the wire with suflicient friction so that it may be pulled through the device and cause a predetermined amount of tension to be applied to the wire.

Next, the wire extends over and wraps around a metallic support or drum 20 the purpose of which is to provide a predetermined amount of capacity between the wire and the support. Preferably the drum has end bells 21 and 22 with shafts 23 which are rotatably supported in brackets 24. I have found that if the drum proper is provided with a predetermined degree of taper that the wire will assume a predetermined position on the drum against the end bell 22. I find that with a drum of the proper size, five turns of wire around the drum will provide a normal capacity of about 150 microfarads to the drum.

From the drum the wire extends to and has one end secured on aferrite rod 30.

The ferrite rod is supported in a lathe like jig comprising a support 31 for the rod at one end and a driven support in the form of a chuck 32 at the other end, the supports being mounted on brackets 33. A second friction means 14 is interposed between the capacity drum and the core, for holding the wire under tension where it is severed.

The end of the wire may be secured to the rod by a piece of tape or clamping ring 34 or it may be secured in the chuck. In either event the end of the wire is grounded at 35.

It will therefore be seen that the wire comes from the supply spool under tension to the capacity drum 20 and is wound under tensiononto the ferrite rod 30, which may take any desired cross sectional form, the most common being round.

The drum 20, and if desired its end bells, may be insulated from ground. A connection is made from the drum to the grid 60 of a vaccum tube which forms a part of an oscillator circuit which may be the wellknown Clapp oscillator. Thus the wire on the drum forms a capacity between the wire and the grid of the oscillator. Inasmuch as the wire is also forming an inductance on the ferrite rod which increases with the increase in amount of wire being wound on the rod, and that inductance is grounded at one end, there is effectively a variable inductance in series with a capacity which provides a series resonant circuit connected to the grid 60. This is schematically indicatedin Fig. 2.

In addition there are provided the usual voltage divided capacitors 70 and 71 connected across the resonant circuit and the mid point being connected to the cathode 73 of the oscillator tube. A choke 74 may be placed in the cathode circuit to ground. The output from the oscillator is connected to a circuit which may include a frequency meter 75.

In operation the wire is wound on the ferrite rod until the frequency meter indicates that the inductance 30' has reached a value to produce a predetermined frequency in the oscillator circuit, which in the circuit is the desired inductance for enabling the antenna to be tuned over a predetermined part of the spectrum determined by the type of receiver in which his to be used. As an example the inductance may be increased until an output frequency of 600 or 800 kc. is attained after which the winding operation ceases and the wire is severed and secured in place by taping or clamping the other end.

The invention lends itself to a more automatic operation in that the output of the oscillator can be connected into a frequency selective circuit, tuned to the desired frequency and the motor automatically shut off when a predetermined inductance is wound on the rod.

It will thus be apparent that I have provided a means for automatically determining the correct amount of wire to be wound on a ferrite rod to provide an antenna having the exact inductance desired for subsequent installation in the antenna circuit of a radio receiver.

Furthermore as indicated the operation once started may be automatically terminated which enables one operator to attend to a bank of these machines and merely reload and remove the articles.

Having thus described my invention in an embodiment thereof it is appreciated that numerous and extensive departures may be made from the disclosure, which is for the purpose of illustration rather than limitation, without departing from the spirit of the invention as defined by the appended claims.

I claim:

1. The method of winding antenna assemblies comprising a ferrite core and a wire inductance which comprises passing the wire in proximity to a metallic element to-prov-ide a predetermined capacity between the element and the wire, winding the wire on the core to provide an inductance which is in series with the capacity to form a series resonant circuit, utilizing the series resonant circuit so formed to control a frequency indicating circuit, and winding wire onthe core until a predetermined frequency is attained.

2. An apparatus for forming iron core antennas which comprises a support for a supply of wire, a support for a core rotatably supporting the core, means to rotate the core support, a coil of wire carried by the wire support and tension means for pulling wire from the support under tension, a capacity drum comprising a metallic surface of tapered formation, said wire being wound around said tapered surface to an extent to provide a predetermined capacity between the wire and the surface, said surface being connected to an oscillator, a second tension means for receiving the wire as it passes off the capacity drum, means to secure said wire on said core, said wire on said core providing an inductance which is determined by the number of turns on the core, and grounding means for grounding one end of the inductance, said capacity and inductance forming a series resonant circuit connected to and controlling the frequency of said oscillator, and control means connected into and operable by said oscillator to shut off the winding means at a predetermined frequency.-

3. Apparatus for forming an inductance of a predetermined value which comprises means for first passing a continuous wire in proximity to a conductive member to provide a predetermined capacitance between the wire and said member and for then winding said wire into a coil having an inductance connected through the wire to said capacitance and forming a resonant circuit therewith, and frequency responsive means coupled to said resonant circuit and responsive to the resonant frequency thereof.

4. Apparatus for forming an inductance of a predetermined value which comprises means for passing a continuous elongated conductor past a conductive member in capacitative relationship to said conductive member and for then forming into an inductance element the portion of said continuous conductor which has moved past said conductive member, and frequency responsive means connected to said elongated conductor and said conduc tive member and responsive to the resonant circuit provided by the capacitance between said continuous conductor and said conductive member and the inductance of said inductance element into which said elongated conductor is formed.

5. Apparatus for forming an inductance of a predetermined value which comprises means for moving a continuous wire past a conductive member in capacitative relationship to said member to provide a predetermined capacitance between the wire and said member and for then winding said wire into a coil which provides an inductance connected to said capacitance and forming therewith a resonant circuit, and frequency responsive means coupled to said resonant circuit to respond to the resonant frequency thereof.

6. Apparatus for making an inductance of a predetermined value which comprises a rotary drum having a conductive periphery, means for passing a continuous insulated wire around said drum a predetermined number of times to establish a preselected capacitance between the wire and the drum and for then passing said wire from the drum and winding said wire into a coil having an inductance which forms a series resonant circuit with said capacitance, and frequency responsive means connected to said series resonant circuit and responsive to the resonant frequency thereof.

7. Apparatus for forming an inductance on a core which comprises a rotary metal drum, a rotatably supported core, a supply of insulated wire, means for winding said wire around the drum a predetermined number of times to establish a preselected capacitance between the wire and the drum and for then passing the wire from the drum and coiling said wire around the core to form therewith an inductance which forms a series resonant circuit with said capacitance, and frequency responsive means connected to said resonant circuit and responsive to the resonant frequency thereof.

8. The apparatus of claim 7, wherein said core is of ferrite.

9. The apparatus of claim 7, wherein said series resonant circuit is connected in an oscillator to determine the oscillation frequency of the oscillator, and wherein there is provided means coupled to the output of the oscillator for 'indicating its oscillation frequency.

10. The apparatus of claim 7, wherein the drum has its periphery tapering inwardly toward one end of the drum and a flange on said end of the drum for locating the wire on the drum.

11. The method of making an inductance of a predetermined value which comprises moving a continuous wire past a conductive element in capacitive relationship to said element to provide a predetermined capacitance between the wire and said element, then winding the wire into a coil to provide an inductance connected to said capacitance and forming therewith a resonant circuit, utilizing the resonant circuit so formed to control frequency responsive means, and terminating the winding of the wire into said coil when a predetermined frequency is established at said frequency responsive means by said resonant circuit.

12. The method of making an inductance of a predetermined value which comprises the steps of passing an insulated wire around a conductive drum a predetermined number of times to establish a preselected capacitance between the wire and the drum, thereafter passing said wire from the drum and winding it into a coil to form an inductance which forms a series resonant circuit with said capacitance, connecting the resonant circuit so formed to a frequency responsive means, and terminating the winding of said coil when a predetermined frequency is established at said frequency responsive means by said resonant circuit.

13. The apparatus of claim 6, wherein there is further provided means for terminating the winding of said wire into a coil when a predetermined frequency is established at said frequency responsive means by said resonant circuit.

References Cited in the file of this patent UNITED STATES PATENTS Grisdale Mar. 27,, 1956 

